1. Technical Field
The present invention relates to curing systems in general, and, in particular, to a method for curing thin films on substrates at low temperatures.
2. Description of Related Art
Printed electronics is the convergence of the semiconductor industry and the printing industry. The notion of printing electronic circuits instead of printing reading materials is seductive to printers as they can see the potential for doing “high value” print jobs without making major changes to their equipment. Similarly, electronic circuit manufacturers view the notion of printing electronic circuits as equally seductive because it allows them to fabricate electronic circuits in large volumes at a relatively low cost.
During the manufacturing of electronic circuits, most thin film coatings need to be thermally processed, and the effectiveness of most thermal curing processes is related to the product of temperature and time. For example, the typical approach to curing a thin film is placing the thin film in an oven set to the maximum working temperature of a substrate on which the thin film is disposed, and allowing the thin film to be cured within some reasonable amount of time.
Since printed electronic circuits are typically associated with high volume and low cost, the substrates for the printed electronic circuits need to be made of relatively cheap materials such as paper or polymer instead of traditional substrate materials such as silicon, quartz, glass, ceramic, FR4, etc. However, paper or polymer has a much lower temperature of decomposition than silicon, quartz, glass, ceramic, FR4, etc., and the much lower temperature necessitates a longer cure time for thin films. For example, the maximum working temperature of polyethylene terephthalate (PET) is 150° C., and a typical curing time for a silver based conductive film at this temperature is in the order of minutes. Such a long curing time makes the proposition of printing electronic circuits on paper on polymer much less economically attractive.
Consequently, it would be desirable to provide a method and apparatus for thermally processing thin films on low-temperature substrates at a relatively high speed.